Simulation and Scientific Computing (Simulation und Wissenschaftliches Rechnen - SiWiR) Winter Term 2014/15 Prof. Dr. Christoph Pflaum, Florian Schornbaum Chair for System Simulation Introductory Lecture Monday, October 6, 2014 Outline • General Information / Organizational Matters People (Lecturer, Tutors, HiWis) • Structure of the Lecture/Exercises • • Motivation (for Scientific Computing) • Topics Lecture • Content of Exercise Classes • Tutorial • • Grading / Evaluation of Exercises Simulation and Scientific Computing (Simulation und Wissenschaftliches Rechnen - SiWiR) Florian Schornbaum - Chair for System Simulation - 2014/15 3 People • Lecturer: Prof. Dr. Christoph Pflaum • Tutors (for the exercise classes): • Florian Schornbaum • Dominik Bartuschat • Student Tutor: • Lorenz Hufnagel (supervision of computer exercises) • Contact: • [email protected] Simulation and Scientific Computing (Simulation und Wissenschaftliches Rechnen - SiWiR) Florian Schornbaum - Chair for System Simulation - 2014/15 4 General Information • Schedule: • Monday, 10:15 – 11:45, lecture, K1-119 • Tuesday, 12:15 – 13:45, computer exercise, 00.131 • Tuesday, 14:15 – 15:45, exercise, 01.151-128 • Wednesday, 14:15 – 15:45, computer exercise, 00.131 • Wednesday, 16:00 – 17:30, exercise, 01.255-128 • ( Thursday, 10:15 – 11:45, tutorial, 00.152-113 ) • No exercises in the first week – exercises start on Tuesday, October 14, 2014! • You have to sign up for both the lecture and the exercises on mein campus until Friday, October 31, 2014! Simulation and Scientific Computing (Simulation und Wissenschaftliches Rechnen - SiWiR) Florian Schornbaum - Chair for System Simulation - 2014/15 5 Exercises / Tutorial • You don’t have to visit the exercise classes … • … but visiting one exercise class per week is strongly encouraged! • Computer exercises are completely optional – If you need assistance for the programming exercises, you can ask the tutors for help during that time. • For the exercises, team formation is mandatory: You have to divide into groups of three persons. • You have to sign up on the team formation list at our chair until Friday, October 31, 2014! • For the tutorial, each student must prepare a 10 minute talk. The talks will be in December/January – Topics will be assigned in October/November. Simulation and Scientific Computing (Simulation und Wissenschaftliches Rechnen - SiWiR) Florian Schornbaum - Chair for System Simulation - 2014/15 6 Organizational Matters • You have to get an account at our chair. • Remote access to our computers (i10cip1.informatik.uni-erlangen.de to i10cip12) is only possible via ssh (Windows users: PuTTY & WinSCP). • Access requires a public-private key pair: [user@private-pc-at-home/laptop ~]$ ssh-keygen -t dsa -b 1024 Create a default key "~/.ssh/id_dsa" and copy (e.g., via mail) the public (!) key located at "~/.ssh/id_dsa.pub" to the "~/.ssh/" directory of your account at LSS. If the directory does not exist at your LSS account, you must create it. Then: [user@i10cip5 ~]$ cat ~/.ssh/id_dsa.pub >> ~/.ssh/authorized_keys • In order to login, you have to either first access a computer from the university network, or log in via VPN: http://www.rrze.fau.de/dienste/internet-zugang/vpn/openvpn.shtml Simulation and Scientific Computing (Simulation und Wissenschaftliches Rechnen - SiWiR) Florian Schornbaum - Chair for System Simulation - 2014/15 7 Outline • General Information / Organizational Matters People (Lecturer, Tutors, HiWis) • Structure of the Lecture/Exercises • • Motivation (for Scientific Computing) • Topics Lecture • Content of Exercise Classes • Tutorial • • Grading / Evaluation of Exercises Simulation and Scientific Computing (Simulation und Wissenschaftliches Rechnen - SiWiR) Florian Schornbaum - Chair for System Simulation - 2014/15 8 Motivation (Scientific Computing) ⇒ video Simulation and Scientific Computing (Simulation und Wissenschaftliches Rechnen - SiWiR) Florian Schornbaum - Chair for System Simulation - 2014/15 9 Motivation (Scientific Computing) Simulation and Scientific Computing (Simulation und Wissenschaftliches Rechnen - SiWiR) Florian Schornbaum - Chair for System Simulation - 2014/15 10 Motivation (Scientific Computing) • Example (3D simulation): • Resolution (after domain discretization): 2,500 × 2,000 × 2,000 • Time steps: 1,000,000 = 106 • Floating point operations per cell/grid point: 100 • Total number of floating point operations required for the entire simulation: 1,000,000,000,000,000,000 = 1018 • Performance of an Intel® Core™ i7-4770 Processor: • Theoretical peak: 217.6 GFLOPS floating point operations per second • Linpack with Intel MKL library: 177 GFLOPS • 1 GFLOPS = 109 FLOPS = 1,000,000,000 FLOPS • Assuming the simulation (~100 GiB) even fits in the main memory of the i7-4770, it would run for at least two months. Simulation and Scientific Computing (Simulation und Wissenschaftliches Rechnen - SiWiR) Florian Schornbaum - Chair for System Simulation - 2014/15 11 Motivation (Scientific Computing) • CPU frequencies cannot get higher (power, heat, …) • Solution: Parallelism • On-chip: superscalar processors, instruction pipelining, … • Multiple cores per processor / multiple processors per system • Multiple interconnected compute nodes ⇒ clusters / supercomputers • One of the fastest supercomputers: Sequoia (IBM BlueGene/Q) • Number of cores: 1,572,864 (6,291,456 threads) • Linpack performance: 17.2 PFLOPS = 17.2 ∙ 1015 FLOPS • Our example simulation would finish in ~10 minutes. • The next generation of supercomputers targets 1 exaFLOPS (EFLOPS) = 1018 FLOPS! (power consumption …) Simulation and Scientific Computing (Simulation und Wissenschaftliches Rechnen - SiWiR) Florian Schornbaum - Chair for System Simulation - 2014/15 12 Outline • General Information / Organizational Matters People (Lecturer, Tutors, HiWis) • Structure of the Lecture/Exercises • • Motivation (for Scientific Computing) • Topics Lecture • Content of Exercise Classes • Tutorial • • Grading / Evaluation of Exercises Simulation and Scientific Computing (Simulation und Wissenschaftliches Rechnen - SiWiR) Florian Schornbaum - Chair for System Simulation - 2014/15 13 Lecture Topics • Code optimization for performance (writing efficient code) • Hardware-aware code optimization • Finite differences for solving differential equations • Solvers: direct solvers & iterative methods • Parallelization (concepts, algorithms, standard programming models/APIs) • Expression templates (C++ metaprogramming technique) • Ray tracing (not for CG but for simulations involving lasers) • … Simulation and Scientific Computing (Simulation und Wissenschaftliches Rechnen - SiWiR) Florian Schornbaum - Chair for System Simulation - 2014/15 14 Exercise Topics • Implementation of topics from the lecture • Programming language: C++ (C++11) • Hardware-aware code optimization: get as much performance as possible out of one core • On-chip parallelization using threads: get as much performance as possible out of one CPU/chip • System parallelization: get as much power as possible out of a cluster/supercomputer ⇒ live demonstration Simulation and Scientific Computing (Simulation und Wissenschaftliches Rechnen - SiWiR) Florian Schornbaum - Chair for System Simulation - 2014/15 15 Tutorial Topics • Talks cover various topics on performance optimization, numerical analysis, simulation, etc. • Some selected topics: • • • • • • • • • Automated empirical optimization of software (ATLAS) uBlas and boost Shortley–Weller discretization (for finite differences) Preconditioners GMRES Domain partitioning/load balancing with METIS Newton–Krylov methods for non-linear problems Runge Kutta methods for ODEs … Simulation and Scientific Computing (Simulation und Wissenschaftliches Rechnen - SiWiR) Florian Schornbaum - Chair for System Simulation - 2014/15 16 Outline • General Information / Organizational Matters People (Lecturer, Tutors, HiWis) • Structure of the Lecture/Exercises • • Motivation (for Scientific Computing) • Topics Lecture • Content of Exercise Classes • Tutorial • • Grading / Evaluation of Exercises Simulation and Scientific Computing (Simulation und Wissenschaftliches Rechnen - SiWiR) Florian Schornbaum - Chair for System Simulation - 2014/15 17 Grading / Evaluation of Exercises • Written exam: • • Sometime in February 2015, 90 minutes Covers topics of the lecture and exercises (including programming) • “Grading” of the exercises: • • • • • • Red, yellow, or green point for each exercise 4 exercises in total To pass exercises you need at least: 3 yellow + 1 green point red + green = 2 x yellow With 2 red points (and without winning a performance challenge), you cannot pass the exercises! Performance challenges: You can win point “upgrades” • Tutorial: • You must be present for all talks Simulation and Scientific Computing (Simulation und Wissenschaftliches Rechnen - SiWiR) Florian Schornbaum - Chair for System Simulation - 2014/15 18 THE END QUESTIONS ?
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